A.T. Robertson Commentary Matthew 18:25

"But forasmuch as he had not [wherewith] to pay, his lord commanded him to be sold, and his wife, and children, and all that he had, and payment to be made." — Matthew 18:25 (ASV)

Had not wherewith to pay (μη εχοντος αυτου αποδουνα). There is no "wherewith" in the Greek. This idiom is seen in Lu 7:42; 14:14; Hebrews 6:13. Genitive absolute though αυτον in the same clause as often in the N.T.

To be sold (πραθηνα). First aorist passive infinitive of πιπρασκω. This was according to the law (Exodus 22:3; Leviticus 25:39,47). Wife and children were treated as property in those primitive times.